Valves employ ceramic discs as valve elements and/or as shut-off elements. Other uses of ceramic discs inside valves include, but are not limited to, throttle elements, elements for regulation or control of gaseous flow or liquid flow, mixing or diverting elements etc. These valves commonly comprise a metallic or a polymeric housing.
The German patent application DE102008017099A1 discloses a valve element with two valve plates 3a, 3b. The valve plates 3a, 3b are arranged perpendicular to flow path through the valve. FIG. 1 of DE102008017099A1 shows U-shaped valve plates 3a, 3b that may slide in opposite directions.
The German patent application DE102008017099A1 teaches in par 12 flange inserts 9 that are made of metal or of plastics. DE102008017099A1 does not teach the use of ceramics in valves. The application does, in particular, not deal with difficulties due to parts such as housings and throttle elements that are made of different materials.
Difficulties due to gaskets made of different materials are, however, known from various other technical fields such as wristwatches. The Japanese patent application JP19970269073 teaches a watch wherein a glass cover 203 is mounted on a packing 300. The arrangement of JP19970269073 employs a gasket 100 to obtain a wristwatch that is waterproof and dustproof.
The European patent application EP2444702A1 discloses a valve with fixed disc 21 and with a moving disc 30. The moving disc 30 can be arranged both upstream and downstream of the fixed disc 21. In accordance with par 33, the surfaces discs 21 and 30 abut one another in order to achieve fluid-tightness.
A fluid-tight arrangement requires the abutting surfaces of the discs 21 and 30 to be planar or substantially planar. To provide surfaces of ceramic discs that meet those requirements, the surfaces are typically grinded and/or polished during manufacture.
The arrangement comprises bearings 40, 41 that connect the moving disc 30 to a channel 24. FIG. 3 of EP2444702A1 depicts bearings 40, 41 that are ball-shaped. The connection between the moving disc 30 and the channel 24 also impacts on fluid-tightness, since the bearings 40, 41 transfer strains from the second channel 24 to the disc 30. The second channel 24 may, for instance, be strained as a result of thermal stresses or as a result of pressures inside and outside the valve.
To come up with a fluid-tight gasket between the discs 21 and 30, those strains need to be reduced to a minimum. The surface of the disc 30 in contact with the disc 21 and the opposite surface of the disc 30 in contact with the bearings 40, 41 require polishing. The requirement of ceramic discs with planar or with substantially planar surfaces adds to the cost of the valve. In addition, the ceramic material needs to be stiff in order to ensure minimum strains of the disc 30.